Sump

What Is a Sump, And What Does a Sump Have to Do with a Home Aquarium?

(The First Tank Guide)

So, what is a sump? A sump is simply a container to collect water
from a plumbed system. So, what does that mean? It means that if you
have tubes and pipes (plumbing) coming out of your tank to carry water
to filters or other equipment, you may need some place for water to
collect. This place for water to collect is your sump.

A sump is not an aquarium
filter. While a sump may contain filters or may house other aquarium equipment, the sump itself doe not
provide any filtration for the fish tank.

Closed or Open Systems

One thing that is important in determining whether you need (or
even want) to get a sump for your home aquarium is whether your fish tank is an open or
closed system.

Most aquariums are closed systems. In a closed system, there is no
place for water to leak out. Canister
filters, ultra-violet sterilizers,
and fluidized bed filters are all closed
systems. Water is taken out of the fish tank through a tube, pumped
through the sterilizer or filter, and returned to a point inside the
tank. This is called a closed system because there isn't any point
along the water's path where it is not controlled and
contained. Closed systems do not need a sump.

Open systems have some means within the system where water could -
or is even expected to - escape. Trickle
filters and protein skimmers are open
systems. These pieces of equipment are designed with openings to allow
the release of water, air, or waste. Because these systems are open,
they need something to catch the water that can (or does) pass
through. Though they can be set up so that this can fall back into the
tank, usually it is the sump that catches this overflow.

Aquarium Water Return

Water is returned from the sump to the main tank. This is
accomplished with a circulation pump placed in the sump (if the pump
is submersible) or plumbed in adjacent to the sump (if the pump is not
submersible).

In most cases, water is pumped from the sump into the aquarium,
and then allowed to flow back into the sump. In this way, the pump is
allowed to run continuously. In some cases, however, there may not
normally be water getting into the sump. In these cases, the pump
needs to be switched on and off as water collects in the sump. This is
normally accomplished with a float switch, similar to the floats that
turned off the water in old-style toilets, or the switches that
automatically turn wells back on when stock water tanks start to get
low.

Sump Size

Since the main reason for having a sump set up with your aquarium
is to keep water (or aquarium waste) from spilling out onto the floor,
you need to make sure that your sump is large enough to do that in the
case of a problem.

In general, this means that your sump needs to hold all the water
that can drain out of the plumbing, filters, or anything else in the
case of a power failure. That doesn't mean that the sump needs to hold
all the water in the tank too, the tank should not be able to drain in
the case of a power failure. The sump just needs to hold all the water
in pipes, plumbing, tubes, or other containers that allow water to
flow into the sump in the first place.

Usually the easiest way to do this is to set things up and get
things running, then turn off the power to the tank and let water
drain into the sump. This will tell you how much water drains out of
everything into the sump. While the power is still off, fill the sump
close to the top. Then turn the power back on. As water is pumped out
of the sump and back into all the systems, you will see the water
level in the sump go down. After everything has been running for a few
minutes, maybe half an hour, you will see the level the water is
lowered to in the sump. This is the HIGHEST level the
water can ever be in the sump and not risk a problem in case of a
power failure. If the sump is the right size for the system you are
running, you should have plenty of water still over the pump to allow
for safe operation. (You will probably want to mark this level somehow
so you know how much water the system can take.)

Remember, in a system with a sump, the overflow in the tank will
keep the water level in the tank constant. Any water that is
evaporating from the system will be missing from the sump, and if you
are not paying attention to this level you can expose the pump and
risk overheating or other problems. Also remember that if you add
water to the system, you will probably not see any meaningful rise in
the water level in the tank - the rise in water level will be in the
sump. Be sure to never fill it above the maximum level you determined
above.

Uses of a Sump

In addition to their primary purpose collecting water (or possibly
waste) and preventing a spill or damage, sumps can also be used to
house unsightly equipment, or equipment that needs to be out of the
tank for some reason.

The most common use of a sump is in conjunction with a trickle
filter. Generally trickle filters are set up to allow water to flow
through the "tower" of the filter and drop into a sump. Water is then
pumped back into the tank to repeat the process.

Sumps are often used to house protein skimmers, though many
skimmers can be set up in the aquarium. The sump provides a location
out of the fish tank for the skimmer, which can be both large and
unsightly. In fact, the higher quality skimmers really can't be set up
in the tank. By setting the protein skimmer up in the sump rather than
out on its own, the sump then can act as a back-up in case you forget
to check the catch as often as you need to.

Once people have a sump connected to their aquarium, the aquarium heater is often one of the first
things moved to the sump. This can also be important if the aquarium
houses particular aggressive of belligerent fish that may damage the
heater. However, you need to be aware that if the heater is in the
sump, it is only indirectly heating the tank, so it is even more
important to monitor the temperature in the sump and in the tank.